Assimilation-Squared has its problems, but I had nothing wrong with the Cybermen making the Borg their bitches. Hell, it seemed almost inevitable.

But Cyberman tech seems so... low-grade compared to Borg tech. Virtually all Borg machinery is fashioned from nanoprobes and is extremely adaptable, whereas the Cybermen's technology seems primitive by comparison. The Cybers don't function as a hive-mind like the Borg, they don't have a billion possible ideas swimming around in a sea of voices, they're all just programmed to think the same thing. Plus Cybermen can't adapt to energy weapons like the Borg can.